SIR estimation in a wireless receiver

Abstract

A method and apparatus removes bias from an initial signal-to-interference ratio (SIR). In an exemplary embodiment, an initial SIR calculator in an SIR processor calculates the initial SIR based on the signal received by the wireless receiver, while an average SIR calculator in the SIR processor generates an average SIR. Using the average SIR, a bias remover removes the bias from the initial SIR.

What is claimed is: 
     
       1. A method of removing bias from an initial signal-to-interference ratio generated by a wireless receiver comprising:
 calculating the initial signal-to-interference ratio based on a signal received by the wireless receiver; 
 generating an average signal-to-interference ratio by calculating a signal correlation matrix based on channel estimates derived from the received signal, and calculating the average signal-to-interference ratio based on the signal correlation matrix and noise statistics derived from the received signal; 
 calculating a scaling factor based on the average signal-to-interference ratio according to: 
 
       
         
           
             
               f 
               = 
               
                 
                   SIR 
                   _ 
                 
                 
                   
                     SIR 
                     _ 
                   
                   + 
                   α 
                 
               
             
           
         
         where  SIR  represents the average signal-to-interference ratio and α represents an offset parameter; and 
         multiplying the initial signal-to-interference ratio by the scaling factor to remove the bias from the initial signal-to-interference ratio. 
       
     
     
       2. The method of  claim 1  wherein calculating the average signal-to-interference ratio based on channel estimates and noise statistics derived from the received signal comprises calculating the average signal-to-interference ratio based on channel estimates and noise statistics derived from despread values of the received signal. 
     
     
       3. The method of  claim 1  wherein the offset parameter is derived from at least one of a count of despread values processed by the wireless receiver to generate the channel estimates and a count of the paths of a multi-path channel processed by the wireless receiver. 
     
     
       4. The method of  claim 1  wherein calculating the average signal-to-interference ratio based on the signal correlation matrix and the noise statistics comprises:
 calculating weighting factors based on the channel estimates; 
 calculating an average signal power based on the signal correlation matrix and the weighting factors; 
 calculating an average noise power based on the noise statistics and the weighting factors; and 
 calculating the average signal-to-interference ratio based on the average signal power and the average noise power. 
 
     
     
       5. The method of  claim 4  wherein the offset parameter is derived from at least one of a count of despread values processed by the wireless receiver to generate the channel estimates and a count of the paths of the multi-path channel processed by the wireless receiver. 
     
     
       6. The method of  claim 1  wherein calculating the initial signal-to-interference ratio based on the received signal comprises calculating the initial signal-to-interference ratio based on the channel estimates and the noise statistics derived from the received signal. 
     
     
       7. The method of  claim 6  wherein calculating the initial signal-to-interference ratio based on the channel estimates and the noise statistics comprises:
 calculating weighting factors based on the channel estimates; 
 generating a signal power estimate based on the weighting factors; 
 generating a noise power estimate based on the weighting factors; and 
 calculating the initial signal-to-interference ratio based on the generated signal and noise power estimates. 
 
     
     
       8. The method of  claim 6  wherein calculating the initial signal-to-interference ratio based on the channel estimates and the noise statistics comprises combining the channel estimates and the noise statistics in an inverse quadratic computer to calculate the initial signal-to-interference ratio. 
     
     
       9. The method of  claim 8  wherein calculating the initial signal-to-interference ratio further comprises:
 calculating a channel estimation matrix based on the signal correlation matrix and the noise statistics; and 
 calculating modified channel estimates based on the channel estimation matrix; 
 wherein combining the channel estimates and the noise statistics in the inverse quadratic computer comprises combining the modified channel estimates and the noise statistics in the inverse quadratic computer to calculate the initial signal-to-interference ratio. 
 
     
     
       10. The method of  claim 1  wherein generating the average signal-to-interference ratio further comprises smoothing past signal-to-interference values associated with the wireless receiver. 
     
     
       11. A method of removing bias from an initial signal-to-interference ratio generated by a wireless receiver comprising:
 calculating the initial signal-to-interference ratio based on a signal received by the wireless receiver; 
 generating an average signal-to-interference ratio by calculating a signal correlation matrix based on channel estimates derived from the received signal, and calculating the average signal-to-interference ratio based on the signal correlation matrix and noise statistics derived from the received signal; 
 calculating a scaling factor based on the average signal-to-interference ratio based on the average signal-to-interference ratio as modified by an offset parameter; 
 multiplying the initial signal-to-interference ratio by the scaling factor to remove the bias from the initial signal-to-interference ratio; 
 calculating a channel estimation matrix based on the noise statistics and the signal correlation matrix; and 
 calculating a different average signal-to-interference ratio based on the channel estimation matrix; 
 wherein calculating the scaling factor based on the average signal-to-interference ratio comprises processing both average signal-to-interference ratios to calculate the scaling factor. 
 
     
     
       12. The method of  claim 11  wherein processing both average signal-to-interference ratios to calculate the scaling factor comprises calculating the scaling factor according to: 
       
         
           
             
               f 
               = 
               
                 
                   
                     SIR 
                     _ 
                   
                   1 
                 
                 
                   
                     
                       SIR 
                       _ 
                     
                     2 
                   
                   + 
                   α 
                 
               
             
           
         
       
       where  SIR   1  represents the average signal-to-interference ratio,  SIR   2  represents the different signal-to-interference ratio, and α represents the offset parameter. 
     
     
       13. The method of  claim 12  wherein the offset parameter is derived from at least one of the channel estimation matrix and a count of despread values processed by the wireless receiver to generate the channel estimates. 
     
     
       14. The method of  claim 11  wherein calculating the initial signal-to-interference ratio based on the received signal comprises calculating the initial signal-to-interference ratio based on the channel estimates and the noise statistics derived from the received signal. 
     
     
       15. The method of  claim 14  wherein calculating the initial signal-to-interference ratio based on the channel estimates and the noise statistics comprises:
 calculating weighting factors based on the channel estimates; 
 generating a signal power estimate based on the weighting factors; 
 generating a noise power estimate based on the weighting factors; and 
 calculating the initial signal-to-interference ratio based on the generated signal and noise power estimates. 
 
     
     
       16. The method of  claim 14  wherein calculating the initial signal-to-interference ratio based on the channel estimates and the noise statistics comprises combining the channel estimates and the noise statistics in an inverse quadratic computer to calculate the initial signal-to-interference ratio. 
     
     
       17. The method of  claim 16  wherein calculating the initial signal-to-interference ratio further comprises:
 calculating a channel estimation matrix based on the signal correlation matrix and the noise statistics; and 
 calculating modified channel estimates based on the channel estimation matrix; 
 wherein combining the channel estimates and the noise statistics in the inverse quadratic computer comprises combining the modified channel estimates and the noise statistics in the inverse quadratic computer to calculate the initial signal-to-interference ratio. 
 
     
     
       18. The method of  claim 11  wherein generating the average signal-to-interference ratio further comprises smoothing past signal-to-interference values associated with the wireless receiver. 
     
     
       19. A signal-to-interference ratio processor in a wireless receiver for removing bias from an initial signal-to-interference ratio, the signal-to-interference ratio processor comprising:
 an initial signal-to-interference ratio calculator to calculate the initial signal-to-interference ratio based on a signal received by the wireless receiver; 
 an average signal-to-interference ratio calculator to generate an average signal-to-interference ratio, said average signal-to-interference ratio calculator comprising:
 a signal statistics estimator to estimate a signal correlation matrix based on the channel estimates; and 
 an average signal-to-interference ratio estimator to calculate the average signal-to-interference ratio based on the signal correlation matrix and the noise statistics; and 
 
 a bias remover comprising: 
 a converter to calculate a scaling factor by modifying the average signal-to-interference ratio by an offset parameter derived from at least one of a count of despread values processed by the wireless receiver and a count of delay paths in a multi-path channel processed by the wireless receiver; and 
 a multiplier to multiply the initial signal-to-interference ratio by the scaling factor to remove the bias from the initial signal-to-interference ratio. 
 
     
     
       20. The signal-to-interference ratio processor of  claim 19  wherein the average signal-to-interference ratio calculator generates the average signal-to-interference ratio based on channel estimates and noise statistics derived from the received signal. 
     
     
       21. The signal-to-interference ratio processor of  claim 20  wherein the average signal to interference ratio calculator derives the channel estimates and the noise statistics from despread values derived from the received signal. 
     
     
       22. The signal-to-interference ratio processor of  claim 19  wherein the average signal-to-interference ratio estimator comprises at least one quadratic computer to calculate an average signal power based on the channel estimates and to calculate an average noise power based on the noise statistics. 
     
     
       23. The signal-to-interference ratio processor of  claim 22  wherein the offset parameter is derived from at least one of a count of despread values processed by the wireless receiver and a count of the paths of the multi-path channel processed by the wireless receiver. 
     
     
       24. The signal-to-interference ratio processor of  claim 19  wherein the initial signal-to-interference ratio calculator calculates the initial signal-to-interference ratio based on channel estimates and noise statistics derived from the received signal. 
     
     
       25. The signal-to-interference ratio processor of  claim 24  wherein the initial signal-to-interference ratio calculator comprises:
 a weight calculator to calculate weighting factors based on the channel estimates; 
 one or more power estimators to generate a signal power estimate and a noise power estimate based on the weighting factors; and 
 a combiner to derive the initial signal-to-interference ratio from the signal power estimate and the noise power estimate. 
 
     
     
       26. The signal-to-interference ratio processor of  claim 24  wherein the initial signal-to-interference ratio calculator comprises an inverse quadratic computer to calculate the initial signal-to-interference ratio based on the channel estimates and the noise statistics. 
     
     
       27. The signal-to-interference ratio processor of  claim 26  wherein the initial signal-to-interference ratio calculator further comprises a channel estimation processor to calculate modified channel estimates based on the channel estimates, wherein the inverse quadratic computer generates the initial signal-to-interference ratio based on the modified channel estimates and the noise statistics. 
     
     
       28. The signal-to-interference ratio processor of  claim 27  wherein the channel estimation processor comprises:
 a channel estimation matrix calculator to calculate a channel estimation matrix based on the noise statistics; and 
 a matrix multiplier to generate the modified channel estimates based on the channel estimates and the channel estimation matrix. 
 
     
     
       29. The signal-to-interference ratio processor of  claim 19  wherein the wireless receiver is disposed in at least one of a mobile station and a base station. 
     
     
       30. The signal-to-interference ratio processor of  claim 19  wherein the average signal-to-interference ratio calculator generates the average signal-to-interference ratio based on the received signal. 
     
     
       31. The signal-to-interference ratio processor of  claim 19  wherein the average signal-to-interference ratio calculator smoothes past signal-to-interference values to generate the average signal-to-interference. 
     
     
       32. The signal-to-interference ratio processor of  claim 19  wherein the average signal-to-interference ratio calculator identifies a target signal-to-interference ratio as the average signal-to-interference ratio. 
     
     
       33. A signal-to-interference ratio processor in a wireless receiver for removing bias from an initial signal-to-interference ratio, the signal-to-interference ratio processor comprising:
 an initial signal-to-interference ratio calculator to calculate the initial signal-to-interference ratio based on a signal received by the wireless receiver; 
 an average signal-to-interference ratio calculator to generate an average signal-to-interference ratio, said average signal-to-interference ratio calculator comprising:
 a signal statistics estimator to estimate a signal correlation matrix based on the channel estimates; and 
 an average signal-to-interference ratio estimator to calculate the average signal-to-interference ratio based on the signal correlation matrix and the noise statistics, the average signal-to-interference ratio estimator comprising a matrix multiplier to square a channel estimation matrix derived from the signal correlation matrix and the noise statistics and wherein the average signal-to-interference ratio estimator estimates a different average signal-to-interference ratio based on the squared channel estimation matrix; and 
 
 a bias remover comprising: 
 a converter to calculate a scaling factor by modifying the average signal-to-interference ratio by an offset parameter derived from at least one of a count of despread values processed by the wireless receiver and a count of delay paths in a multi-path channel processed by the wireless receiver; and 
 a multiplier to multiply the initial signal-to-interference ratio by the scaling factor to remove the bias from the initial signal-to-interference ratio. 
 
     
     
       34. The signal-to-interference ratio processor of  claim 33  wherein the offset parameter is derived from at least one of the channel estimation matrix and a count of despread values processed by the wireless receiver. 
     
     
       35. The signal-to-interference ratio processor of  claim 33  wherein the initial signal-to-interference ratio calculator calculates the initial signal-to-interference ratio based on channel estimates and noise statistics derived from the received signal. 
     
     
       36. The signal-to-interference ratio processor of  claim 35  wherein the initial signal-to-interference ratio calculator comprises:
 a weight calculator to calculate weighting factors based on the channel estimates; 
 one or more power estimators to generate a signal power estimate and a noise power estimate based on the weighting factors; and 
 a combiner to derive the initial signal-to-interference ratio from the signal power estimate and the noise power estimate. 
 
     
     
       37. The signal-to-interference ratio processor of  claim 35  wherein the initial signal-to-interference ratio calculator comprises an inverse quadratic computer to calculate the initial signal-to-interference ratio based on the channel estimates and the noise statistics. 
     
     
       38. The signal-to-interference ratio processor of  claim 37  wherein the initial signal-to-interference ratio calculator further comprises a channel estimation processor to calculate modified channel estimates based on the channel estimates, wherein the inverse quadratic computer generates the initial signal-to-interference ratio based on the modified channel estimates and the noise statistics. 
     
     
       39. The signal-to-interference ratio processor of  claim 38  wherein the channel estimation processor comprises:
 a channel estimation matrix calculator to calculate a channel estimation matrix based on the noise statistics; and 
 a matrix multiplier to generate the modified channel estimates based on the channel estimates and the channel estimation matrix. 
 
     
     
       40. The signal-to-interference ratio processor of  claim 33  wherein the average signal-to-interference ratio calculator smoothes past signal-to-interference values to generate the average signal-to-interference.